title: A heterologous immunoglobulin chain recombinant carries a distinct site for dinitrophenyl and obeys the common hapten binding mechanism.
abstract: A heterologous recombinant of the immunoglobulin alpha heavy chain derived from MOPC-460 and the lambda light chain from MOPC-315 was prepared. This H460L315 hybrid binds N epsilon-(2,4-dinitrophenyl)-L-lysine (DNPL) with an affinity of 1.6 X 10(4) M-1 (7 degrees C). This Ig-hapten complex exhibits an absorption spectrum which is different from those observed for each of its parent-DNPL complexes. Very small quenching is caused in the intrinsic fluorescence of the hybrid upon hapten binding, as contrasted by the large quenching of the parent molecules. Chemical relaxation kinetic measurements show that H460L315 exists in solution in two conformations which exchange with a relaxation time of 20 ms (7 degrees C). This transition is accompanied by a change in the fluorescence quantum yield of the protein. DNPL binds to both conformers at comparable fast, though not diffusion-controlled, rates. The equilibrium between the two conformers is shifted upon hapten binding, and the two complexes exchange at a faster rate than the free protein conformers. Thus H460L315 carries a new binding site for DNPL but follows the common mechanism of hapten binding as that observed for other immunoglobulins. These properties of the hybrid should be closely related to the interactions between its constituting domains.
mesh_terms: D000818:Animals; D002460:Cell Line; D004140:Dinitrophenols; D006241:Haptens; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental / Q000276:immunology; D010954:Plasmacytoma / Q000276:immunology; D055503:Protein Multimerization; D013053:Spectrophotometry; D013816:Thermodynamics
chemical_list: D004140:Dinitrophenols; D006241:Haptens; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains